The invention concerns a water-based pigmented preparation, its production and use and its application in capillary storage systems.
Water-based liquid preparations, so-called inks, have been known for many centuries. While at the time of the Egyptians such inks were mixed for example with soot and thickened with gum arabic it was already in the third century AD that the first oak gall ink was produced by boiling oak apples with iron sulphate, and it already left a quite permanent colouring behind on the application area. Developments further followed, such as inks with water-soluble dyestuffs and even pigments. After production thereof those water-based preparations were filled in small flacons and could be removed therefrom for example with a fine brush or a quill and thus served as a writing implement or however, depending on the choice of raw material, as a makeup implement, that is to say as a cosmetic ink, for example for colouring the eyelids, the lips or for artistically decorating other parts of the skin, and thus referred to in modern fashion as a tattoo. What is common to those systems which are still often used nowadays is that they contain the colouring substance in dissolved or dispersed form in a liquid which often includes water as the main constituent. While water-soluble dyestuffs are present dissolved in polar solvents, that is to say also water, and thus form a single-phase system, pigments are generally present in the form of an undissolved component in the water phase and therefore form a suspension. A disadvantage with water-based inks with soluble dyestuffs is that in-depth coverage is generally not possible. After drying out at the application area the dyestuff solution always allows the underlying surface to shimmer therethrough. A covering colour layer generally therefore cannot be achieved. In addition dyestuff systems have a tendency to so-called colour drifts, that is to say the colour changes with the storage time, in particular under the influence of light and temperature. The choice of dyestuff is also markedly reduced in comparison with the available pigments.
To produce intensive, multi-coloured, permanent and covering colour shadings, the use of pigments is absolutely essential. Pigments are almost inert in water, and therefore generally do not react under normal conditions with protic solvents, but after evaporation of the solvent form an intensive colour layer which covers the surface depending on the respective pigment content and which lies on the application surface. A disadvantage with pigment-bearing suspensions is that suspensions generally have a tendency to sedimentation. Consequently, because of the relatively high density, the pigments settle in the storage container in the form of a bottom sediment and in time form a solid pigment cake which is difficult to re-disperse. The ink thus loses its colouring properties as the settled pigments can generally no longer be put back into the surrounding liquid in a residue-free fashion. Even with so-called mixing balls or other re-dispersion aids it is often no longer possible to restore the original homogeneity of the ink. Frequently therefore the viscosity of the liquids is increased with rheology additives, usually xanthan gum, gum arabic, acrylic acid thickeners and others until the liquid has attained a gel-like consistency so that settling or sedimentation of the undissolved substances no longer occurs or occurs only to a slight degree. Because of the high viscosity however not only is it more difficult to get the ink out of the storage container but also application in itself is more difficult for the gelatinous material preferably collects at the tip of the applicator device, in the simplest case a brush or a tapered foam tip, and can therefore be only irregularly distributed. The delivery of colour is non-homogeneous, with coverage in the first part of the stroke being markedly stronger while in the second part of the stroke it loses intensity to a considerable degree. Constant uniform delivery of colour is not possible in that way.
To permanently stabilise the colour at the location of application, film-forming agents, that is to say generally film-forming polymers, are frequently used, which after the volatile substances have dried out, leave behind a permanent coloured film. It is desirable for that film in the best-case scenario to be both water-resistant and also rubbing-resistant. Hitherto however it has not been possible to satisfactorily achieve that in purely water-based inks. Current film-forming polymers such as for example polyvinyl alcohols, polyacrylates or polyvinyl pyrrolidones can admittedly be uniformly incorporated into water-based preparations by virtue of their good water-solubility, but they do not form a water-resistant film. The films formed can be easily dissolved off again by wetting with water. It is thus not possible to achieve sufficient resistance to water and rubbing in respect of the coloured films which are formed. Those polymers which could provide permanent water resistance, namely those which are not soluble in water but are only dispersible therein, are also not sufficiently water-soluble to give a homogeneous mixture with the water-based preparation. Those polymers have a tendency to flocculate out, settle or agglomerate in the form of a non-homogeneous constituent, and that has a detrimental effect on the properties of the preparation. To increase compatibility of the water-dispersible film-forming polymer with a water-based preparation, dispersing aids, that is to say in the simplest case surfactants, are added either to the polymer pre-mixture, the so-called polymer dispersion, or however to the water-based preparation itself. Those dispersing aids are also used to provide for better spreading of the preparation at the location of application. Surfactants however reduce the water resistance of the films which are formed and thus detrimentally affect the water and rubbing resistance of the applied preparation.
A development of applicator devices inter alia for reducing settlement or separation of inks and for simplifying their storage and application are systems with capillary storage means. A capillary storage means is a device which includes a porous fibre-like material which has interconnected cavities which preferably have a through-flow direction, namely in the longitudinal direction of the storage means. Suitable materials are for example specific polyester, polyamide or cellulose acetate fibres which are enclosed by a cylindrical film which serves as a casing and thus as a non-spill protection. That storage means is then saturated with the colouring liquid and stores it in the cavities in the interior thereof. Ink flows out of the storage means by the contact of an end of the storage means with the application area, in which case a supplementary delivery of ink is possibly also provided at the same time from a supply storage means disposed on the opposite side. Because of the very small cavities and ducts for transport of the liquid the known pigment-bearing preparations are hitherto not suitable for such storage means. In conventional water-based preparations or inks, even if the pigments can be set to a sufficiently small particle size, the pigments are not sufficiently permanently stabilised with that small particle size of a few micrometres, but reagglomerate instantaneously, which inevitably leads to blockage of the capillary storage means. Therefore in the writing implement industry and also in cosmetics, capillary storage systems are mainly filled with inks involving soluble dyestuffs, single-phase systems which however present the above-mentioned disadvantages such as lack of colour coverage, colour drifts and also so-called ‘staining’, permanent penetration into and colouring of the parts of the skin, as frequently occurs precisely in cosmetic preparations.
Therefore the problem of the invention is to provide a water-based pigmented preparation which overcomes the disadvantages in the state of the art. The preparation is to be permanently stable, that is to say it is neither to settle, sediment or separate, but is to be easily re-dispersible, without a noticeable application of force. In addition the preparation is to afford water-resistant and rubbing-resistant films. The preparation is to be capable of use with current capillary storage systems and is such that it can be applied by simple application, and it is to have excellent homogeneous colour delivery and colour adhesion.
A further problem of the invention is to provide a process for the production of the preparation.